For example, an electric power steering system installed in a vehicle is provided with an electric motor control apparatus that controls driving of an electric motor. As disclosed in, for example, JP 2014-151850 A, JP 2013-106376 A, JP 2013-63689 A, JP 2015-134598 A, and JP 2014-189166 A, the electric motor control apparatus includes a driver circuit that drives the electric motor, a control circuit that controls the driver circuit, and an external connector for establishing electrical connection with an external apparatus.
In general, the driver circuit through which great current passes is implemented on a metal board or a metal-made cabinet, in consideration of heat dissipation, safety and the like. On the other hand, the control circuit through which great current does not pass is implemented on a printed circuit board (control board) or the like in consideration of high-density packaging and the like.
In JP 2014-151850 A, the driver circuit is implemented on one surface of the metal board. In order to dissipate heat from a heat-generating component included in the driver circuit and from the metal board, the metal board is fixed to a metal-made lid (cover) so that other surface of the metal board is in contact with the back surface of the lid. The printed circuit board equipped with the control circuit is fixed to the inside of a storage of the cabinet (case). By the lid being engaged with the cabinet so as to close the storage, the metal board and the printed circuit board are stored in the storage. In the storage, the metal board and the printed circuit board oppose to each other in parallel, and are electrically connected to each other by a connecting terminal. The electric motor is installed on the cabinet oppositely to the storage. On one surface of the printed circuit board not opposing to the metal board, a rotation sensor that detects rotation of a rotation shaft of the electric motor is mounted. The external connector is fixed to the cabinet on the side where the electric motor is installed. A plurality of terminals of the external connector project inside the storage of the cabinet and are electrically connected to the printed circuit board and the metal board.
In JP 2013-106376 A, the driver circuit is separately implemented on a first board and on a second board. The first board and the second board are electrically connected to each other by a connecting terminal retained by a relay member. The control circuit is implemented on a third board. On one surface of the third board which one surface does not oppose to the first board and the second board, a rotation sensor is mounted. The first board is fixed to the inside of a storage of a unit cover, so that one surface of the first board which one surface is not equipped with the driver circuit is in contact with the back surface of the unit cover. The second board is fixed inside the unit cover via the relay member and the first board. The third board is fixed to a plurality of pedestals provided inside the unit cover. By the unit cover engaging with the motor cover, the first to third boards and the relay member are stored inside the unit cover. The external connector is fixed to the outer surface of the unit cover, which outer surface is on the side opposite to the electric motor. A plurality of terminals of the external connector penetrate through the unit cover and are electrically connected to the second board or the third board.
In JP 2013-63689 A, the driver circuit is separately implemented on the metal board and on a second printed circuit board. The control circuit is implemented on a first printed circuit board. The metal board is fixed inside a storage of the cabinet (housing) so that one surface of the metal board which one surface is not equipped with components is in contact with the inner surface of the cabinet. The first printed circuit board is disposed on other surface side of the metal board. The second printed circuit board is disposed oppositely to the metal board with reference to the first printed circuit board. The metal board, the first printed circuit board, and the second printed circuit board are electrically connected to one another by a connecting terminal. By the cabinet and the lid engaging with each other so as to close the storage of the cabinet, the metal board, the first printed circuit board, the second printed circuit board and the connecting terminal are stored inside the storage. The electric motor is installed on the cabinet oppositely to the lid. The external connector is projectively and integrally provided at the outer surface of the lid, which outer surface is on the side opposite to the cabinet. A plurality of terminals of the external connector penetrate through the lid and are electrically connected to the first printed circuit board or the metal board.
In JP 2015-134598 A, the driver circuit is implemented on the control board as a module. The module is thermally in contact with a heat sink via a heat conductive member. The control board is fixed to a motor cover such that one surface of the control board which one surface is on the side opposite to the module is in contact with the upper surface of the motor cover. The motor cover stores the electric motor. By the heat sink being held between the motor cover and a connector case, the control board and the module are stored between the motor cover and the heat sink. Between the heat sink and the connector case, a capacitor and a noise filter module are stored. The external connector is projectively and integrally provided at the outer surface of the connector case which outer surface is on the side opposite to the motor cover. A plurality of terminals of the external connector penetrate through the cover and the heat sink and are electrically connected to the control board.
In JP 2014-189166 A, the driver circuit is implemented on a first board. The control circuit is implemented on a second board. The first board is disposed on the inner side of a relay member, and fixed to the inner surface of a unit cover together with the relay member. One surface of the first board where the driver circuit is not implemented is in contact with the inner surface of the unit cover. The second board is fixed to the relay member on the side opposite to the unit cover. A rotation sensor is mounted on a surface of the second board not opposing to the first board. The first board and the second board are electrically connected to each other by a connecting terminal. By the unit cover engaging with the motor cover, the first board, the second board, and the relay member are stored inside the unit cover. At the circumferential surface of the relay member, the external connector is projectively and integrally provided. The external connector laterally projects relative to the motor cover and the unit cover. A plurality of terminals of the external connector penetrate through the relay member and are electrically connected to the first board or the second board.
In connection with the electric motor control apparatus, implementing the driver circuit dispersedly on a multitude of members such as boards, a heat sink and the like increases the number of components. This disadvantageously increases the number of processes in assembling, and increases the size of the electric motor control apparatus in the direction in which the boards and the heat sink are arranged. Further, as in JP 2014-151850 A, when the mating part of the external connector projects to the side where the electric motor is provided, the external connector must be disposed laterally relative to the electric motor with a distance, so that connecting the harness to the mating part is not hindered by the electric motor. However, such a disposition laterally increases the size of the electric motor control apparatus. Further, the board must be increased in size for connecting the terminals of the external connector. This also laterally increases the size of the electric motor control apparatus.
Further, assembling the electric motor control apparatus includes: connecting the external connector and the connecting terminal to the boards; fixing the boards and the external connector to the cabinet and the lid; and combining the cabinet with the lid. Performing these operations without visual monitoring will result in poor assembling work efficiency and erroneous assembling. That is, assemblability disadvantageously reduces.